Path for tags in VIM for multiple projects

Question

Hi,

I've recently started using ctags on my projects. I currently have the following setup:

root/tags [contains all non-static tags]
root/foo/tags [contains static tags for the foo directory]
root/bar/tags [static]
root/something/else/tags [etc.]
...

I can set tags=./tags,tags,/path/to/root/tags and everything works perfectly.

However, my problem is that I work on several projects at once, so I have, for example, /path/to/root1, /path/to/root2, and /path/to/root3 all at once. I'd rather not manually set the tags each time I open a file; is there any way I can have tags to to the /path/to/rootX based on the file I'm editting? (i.e., if I'm editing /path/to/root3/foo/x.c, use the tags in root3/tags?

In my case, all of my projects share a common parent directory; what I really want is something like:

set tags=./tags,tags,substitute("%:p:h", "\(^\/path\/to\/.*/\).*$", "\1", "")

but I can't seem to get the right vimfu to make it work.

EDIT: I just realized that this won't work; I can't actually write to root*. Instead, I'd like to store my main ctags file in ~/ctags/root*/tags, where there's a 1:1 mapping between the subdirectories of ~/ctags/ and /path/to/ [For those who may be wondering, these are ClearCase UCM dynamic views; neither /view/XXX/ nor /view/XXX/vobs/ is writable]

Answer 1

If what you want is:

set tags=./tags,tags,substitute("%:p:h", "\(^\/path\/to\/.*/\).*$", "\1", "")

Try:

let &tags = './tags,tags,' . substitute(expand("%:p:h"), "\(^\/path\/to\/.*/\).*$", "\1", "")

There's no expansion in a :set command. Also, "%:p:h" won't be expanded automatically, so use expand(). See:

:help :let-option
:help expand()